Transmission of confidential messages can be vulnerable to security attacks. In passive security attacks, an eavesdropper can listen to the transmission between the transmitter and a legitimate receiver of the transmitted information to reveal the confidential message being transmitted. Various cryptographic encryption schemes have been used to achieve confidentiality. However, use of such cryptographic encryption schemes typically requires generation, distribution and management of keys to encrypt the confidential message.
Applications of a wiretap channel model to physical-layer security have been considered, but relatively few constructive and low complexity coding schemes have been developed. Also, recent efforts exploiting powerful families of error-control codes have met some success in certain cases. For instance, low-density parity check codes (LDPC) have been shown to provide secrecy over erasure channels, while Polar codes and invertible extractors have been proven to ensure secrecy over some symmetric channels. Various results also suggest the usefulness of LDPC codes and lattice codes over a Gaussian wiretap channel. However, such constructions typically only apply to memoryless wiretap channels with full statistical knowledge of the eavesdropper's channel, which can limit their scope of applications.
In this regard, secure communication schemes that utilize the difference between the channel conditions of the legitimate users and eavesdroppers have been proposed. However, with various secure communication schemes, an eavesdropper can have access to only one of two parallel links for the secure communication.
Thus, it is desirable that a secure communication scheme provide for secure communications of information over a compound channel as can provide another level of security in the physical layer as can be over that of existing cryptographic security mechanisms in the application layer.
Further, it is desirable that a secure communication scheme provide for secure communications of information by a coding scheme that provides secrecy over a compound wiretap channel in which an eavesdropper can only observe one of two channels.
Thus, an encryption apparatus and method for secure communication solving the aforementioned problems is desired.